This invention relates generally to roll baling machines typically referred to as round balers which form cylindrical roll bales of crop material and, in particular, to a bal density control system for such roll baling machines.
Hydraulic systems have been used on round balers in the past to control bale density. For example, U.S. Pat. No. 3,722,197 discloses such a hydraulic system for round balers in which double acting cylinder assemblies are utilized for controlling movement of a belt tensioning unit in order to control the density of the formed bales. A drawback of the hydraulic system disclosed in U.S. Pat. No. 3,722,197 is that it is too complex and too expensive when compared with conventional tension springs which have also been used on round balers for effectively controlling bale density.
The present invention provides a system for controlling bale density in a round baler having a frame with arm means mounted on the frame carrying conveying means for forming crop material into roll bales. The arm means is movable between a bale starting position and a full bale position.
The system of the present invention includes a single acting hydraulic cylinder unit connected between the frame and the arm means, a reservoir in fluid communication with the hydraulic cylinder unit, and a control valve for permitting fluid flow from the hydraulic cylinder unit to the reservoir only when the fluid pressure in the hydraulic cylinder unit reaches a preselected level. In the preferred embodiment of the system, the movement of the arm means from the full bale position to the bale starting position causes extension of the hydraulic cylinder unit which results in fluid flow from the reservoir into the hydraulic cylinder unit.